Oskar Groening's 2015 conviction for aiding murders as the "bookkeeper of Auschwitz" was upheld by Germany's highest court Monday.

Groening, 95, had been found guilty of aiding and abetting the murders of some 300,000 Jews at Auschwitz in the 1940s, with officials charging that he was part of the "machinery of death," the BBC News reported. During trial in Luenberg last year, he was accused of helping the camp run efficiently and collecting money stolen from its victims to help the Nazi cause.

Groening was a former Nazi SS officer but did not participate in any of the murders at the Poland camp, which was controlled by the Nazis, Reuters said. He was sentenced to four years in prison for the crime.

The court also rejected appeals from others convicted of the more serious charge of being an "accomplice" to murders.

"It is never too late for justice," German Justice Minister Heiko Maas said in a statement, according to Reuters. "When it comes to the legal processing of Auschwitz there can also never be an end."

Prosecutors are weighing whether Groening is healthy enough at 95 to serve his sentence, the BBC News said. Groening had expressed regret for his work and spoke openly of his experiences at Auschwitz to counter Holocaust deniers.

Former Ohio factory worker John Demjanjuk became the first person convicted in Germany for serving as a death camp guard without any evidence of being involved in a specific killing in 2011, according to the BBC News.

Demjanjuk had denied serving at the Sobibor camp and died in 2012 before his appeal could be heard.